PROJECT SUMMARY Adolescence is a developmental stage of physical and psychological maturation that is preceded by and includes changes in sleep. It is also a critical period associated with the onset of psychiatric disorders. However, how a child's sleeping brain predicts the development of psychopathology, including neurocognitive and emotional disorders, later on during adolescence remains poorly understood. In order to bridge this gap, we have collected preliminary data that suggests that changes in brain activity during specific sleep periods and stages of sleep are significantly associated with sleep disorders and executive deficits and internalizing symptoms in children, adolescents and young adults. Importantly, this project will expand on our previous work in this area by giving us the opportunity to conduct longitudinal analyses of the Penn State Child Cohort, a population-based sample of 700 young children, who participated in a comprehensive sleep study, and neurocognitive, behavioral and medical assessment. This study will provide us with novel findings on the association of changes in brain activity during sleep, typically neglected in routine clinical practice, with cognitive and emotional processes that are present across multiple psychiatric disorders. It will also enable us to test the novel hypothesis that changes in brain activity during sleep are associated with increased risk for the development of neurocognitive disorders and psychopathology during this important transitional period.